In a conventional clean booth as a cleaning space, as disclosed in, e.g., Japanese Patent Application Laid-open No. 1990-4145, there has been adopted a method by which clean air supplied from an HEPA (High Efficiency Particulate Air) filter or a ULPA (Ultra Low Penetration Air) filter set on a ceiling of a box-like body blows down foreign particles and these foreign particles are discharged to the outside from a grating floor formed of a perforated plate. In recent years, however, in a manufacturing process for a sheet-like electronic component as typified by a semiconductor wafer with a wire width of 1 μm or below from which contamination due to grained foreign particles or organic matters must be completely eliminated, a highly cleansed clean booth called a mini-environment has been used. As an example of this type of booth, in Japanese Patent Application Laid-open No. 2001-244315, although an apparatus which computer-controls a displacement volume by providing an exhaust system to a body of a conveying robot as a foreign particle generation source is proposed, but its quantitative effect is not described.
When a robot which may possibly generate dust is not used, although a class 10 or a lower class is achieved with respect to dust of 0.3 μm in an apparatus disclosed in, e.g., Japanese Patent Application Laid-open No. 2000-161735, this value is not sufficient when processing a semiconductor wafer whose wire width is not more than 0.5 μm. Further, in the apparatus disclosed in Japanese Patent Application Laid-open No. 2001-244315, there is a case in which a robot or an opening/closing door as a foreign particle generation source moves in a clean booth or a case in which foreign particles soar above with eddy currents generated on the rear side of a sheet-like matter, a cleanness is insufficient, and installation of an expensive computer-controlled system increases a facility cost, which is not desirable.